A KJ-200 airborne early warning and control plane, at left. A similar plane was involved in the ‘unsafe encounter’.
Photograph: Mark Schiefelbein/AP

A Chinese military aircraft had an “unsafe” encounter with a US navy surveillance aircraft near a contested reef in the South China Sea, according to the US Pacific command.

The two planes came within 1,000ft (300 meters) of each other during Wednesday’s incident near the Scarborough shoal, which is claimed by both the Philippines and China, according to Pentagon spokesman Jeff Davis.

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The close encounter comes amid heightened tensions between the USand China over Beijing’s moves to establish a presence in disputed areas of the South China Sea by building out reefs and atolls into artificial islands.

“On February 8 (local), an interaction characterized by US Pacific command as ‘unsafe’ occurred in international airspace above the South China Sea between a Chinese KJ-200 aircraft and a US Navy P-3C aircraft,” said US Pacific command spokesman Rob Shuford.

“The US Navy P-3C was on a routine mission operating in accordance with international law.”

Davis said the Chinese aircraft essentially “crossed the nose” of the American plane, causing it to “make an immediate turn”.

“We don’t see any evidence that it was intentional,” the spokesman said.

“Clearly we have our disagreements with China over militarization of South China Sea,” he said, but interactions between ships and planes “are largely professional and safe”.

“This seems to be a one-off.”

The KJ-200 is an airborne early warning and command plane while the P-3 is a maritime surveillance aircraft.

The Pacific command said it would address the issue “in appropriate diplomatic and military channels”.

China asserts sovereignty over almost all of the resource-rich region despite rival claims from sout-east Asian neighbors and has rapidly built reefs into artificial islands capable of hosting military planes.

Under Barack Obama’s administration, Washington insisted it was neutral on the question of sovereignty over the South China Sea islets, reefs and shoals, calling for the disputes to be resolved under international law.

But the US has dispatched aircraft and naval patrols to assert its rights of passage through international spaces.